1. Technical Field of the Invention
This invention relates to telecommunication systems and, more particularly, to an integrated radio telecommunications network which interworks circuit switched services and packet switched services, and to a method of interworking an ANSI-41 radio telecommunications network and the General Packet Radio Service (GPRS) packet data network.
2. Description of Related Art
Two approaches to data switching are circuit switching and packet switching. Plain old telephone service (POTS) and cellular voice services, for example, use circuit switching. Fixed circuit switching paths are set up between the parties involved in a call by exchanging signaling messages which contain the parties"" addresses and request the establishment of a physical switching path. The signaling messages are exchanged between the addressees and switching centers, and between switching centers. The switch(es) respond to the requests in the signaling messages by establishing the physical switching path between the addressees. A data switch can be set up in a similar manner to provide circuit switched data services.
Packet switching, on the other hand, utilizes data packets which are comparatively short blocks of message data. The packets may be of fixed length as in asynchronous transfer mode (ATM), or may be of variable length as in frame relay or the Internet protocol (IP). Complete data messages are broken down into short packages, each with a header. These packets may be sent on diverse routes to their eventual destination. Because packets often travel on diverse routes, they may not arrive at the far-end receiving node in sequential order. Thus, the far the end node must have the capability to store incoming packets and rearrange them in sequential order. The destination node reformats the message as it was sent by the originator and forwards it to the final destination user. Packet switching can be considerably more efficient when compared to circuit switching due to the multiplexing effects which make better use of the available transport bandwidth. Each service or user utilizes only the bandwidth it needs, leaving the unused bandwidth for other services/users. A plurality of paths must exist from the originating node to the destination node for in-service performance since an alternate route may be utilized in the event of failure or congestion of a given route.
GPRS is a packet data transmission service which is designed to function with the Global System for Mobile Communications (GSM) to enable mobile stations (MSs) to access both voice/circuit switched and packet data network services. A proposed GPRS packet data standard defines MS service classes and infrastructures to enable MSs to utilize the GPRS network. However, the GPRS standard addresses interworking requirements for GSM, but does not address interworking requirements for radio telecommunications networks based on ANSI/TIA standards such as those utilized throughout most of North America. The network architecture and the interface between the packet-data-specific nodes and the circuit-switched-specific nodes is tailored to GSM. GPRS does not fit within the ANSI-41 network. A system and method of interworking GPRS and ANSI-41 networks is needed so that the full GPRS functionality (e.g., services, interface protocols, node functionality, etc.) can be supported from the perspective of radio access logic, network logic, and service logic in ANSI-41 networks.
Today, ANSI-41 and ANSI-136 networks only provide voice or circuit-switched services. Therefore, an operator cannot benefit from the advantages and flexibility that packet switching provides when the operator is providing Internet access to subscribers utilizing ANSI-41/136-based cellular networks. A dial-up direct access connection or an analog modem connection must be made to the Internet. For a dial-up direct access connection, for example, a circuit-switched connection is provided between a MS and an Internet access gateway. A call is set up to the gateway, and then a Transaction Control Protocol/Internet Protocol (TCP/IP) session to an Internet provider is set up on top of that connection. This solution does not provide the benefits of multiplexing over the air interface and through circuit switching facilities since dedicated resources are utilized for the duration of the Internet connection. This is very inefficient since, in a typical Internet connection, packets of data are not continuously being sent over the connection. Thus, a voice channel over the air interface is tied up for the duration of the Internet connection, and associated circuit-switched resources over the network are not optimally utilized.
The existing solution is also not very flexible in terms of packet data network access because only one connection can be made at a time. It is not possible to make multi-party call connections for data calls in the way that multi-party voice connections can be made. Thus, simultaneous circuit switched voice and data services cannot be provided while connected through a circuit-switched connection to the Internet. If a voice call is routed to a mobile station during an Internet session, the subscriber cannot take the call and then resume the Internet connection in a seamless fashion. The voice call must be rejected, routed to voice mail, or routed to another number. Additionally, the user cannot originate voice calls during a data call because the data call is circuit-switched between the mobile station and the Internet access gateway.
In order to overcome the disadvantage of existing solutions, it would be advantageous to have a method of integrating GPRS packet switched services and infrastructure with the ANSI-41 circuit switched services and infrastructure, thus enabling similar services to those available in GSM. The present invention provides such a method and integrated network.
In one aspect, the present invention is a method of integrating a circuit switched radio telecommunications network having a circuit switched serving node, with a packet switched data network having a packet switched serving node. The method includes the steps of (1) providing a first interface between the circuit switched serving node and an interworking function, (2) mapping in the interworking function, signaling from the circuit switched service node into signaling in a standard packet data network protocol, and (3) sending the mapped signaling from the interworking function to the packet switched serving node utilizing the standard packet data network protocol. In one embodiment, the circuit switched radio telecommunications network is an ANSI-41 radio telecommunications network, and the packet switched data network is a General Packet Radio Service (GPRS) packet data network. The circuit switched service node is a mobile switching center/visitor location register (MSC/VLR) which may be a serving MSC or a gateway MSC. The packet switched service node is a serving GPRS switching node (SGSN).
The method may also comprise the step of connecting to the MSC/VLR, a GPRS/ANSI-136 base station which operates in accordance with both ANSI-136 standards and GPRS standards. A second interface is provided between the SGSN and an interworking GPRS base station controller which adapts a signaling format utilized on the second interface into an air interface signaling format. The adapted signaling is sent from the interworking GPRS base station controller to the GPRS/ANSI-136 base station over a traffic interface. The traffic interface passes through a semi-permanent connection in the MSC/VLR. A third interface is provided between the interworking GPRS base station controller and the MSC/VLR to connect a radio resource management entity (RRME) in the MSC/VLR with an associated component in the interworking GPRS base station controller.
The method further comprises providing an authentication center interface between an ANSI-41 home location register/authentication center (HLR/AC) and a GPRS home location register/authentication center (HLR/AUC). The authentication state of a mobile station operating in both the ANSI-41 network and the GPRS network is sent between the ANSI-41 HLR/AC and the GPRS HLR/AUC utilizing the authentication center interface.
In another aspect, the present invention is an integrated radio telecommunications network which interworks an ANSI-41 circuit switched network and a General Packet Radio Service (GPRS) packet data network. The integrated radio telecommunications network includes a mobile switching center/visitor location register (MSC/VLR) in the ANSI-41 network that provides circuit switched services to a mobile station which operates in both the ANSI-41 network and the GPRS network, and a serving GPRS switching node (SGSN) in the GPRS network that provides packet switched services to the mobile station. An interworking function interfaces the MSC/VLR with the SGSN by mapping control signaling utilized by the MSC/VLR into GPRS packet switched signaling utilized by the SGSN, and mapping GPRS packet switched signaling into circuit switched signaling. An interworking GPRS base station controller interfaces the SGSN with a GPRS/ANSI-136 base station which supports both ANSI-136 operations and GPRS operations. The interworking GPRS base station controller adapts a signaling format utilized by the SGSN into an air interface signaling format utilized by the GPRS/ANSI-136 base station. An interface is provided between the interworking GPRS base station controller and the MSC/VLR to connect a radio resource management entity (RRME) in the MSC/VLR with an associated component in the interworking GPRS base station controller.
The integrated network may also include an ANSI-41 HLR/AC, and a GPRS HLR/AUC. An authentication center interface between the ANSI-41 HLR/AC and the GPRS HLR/AUC sends the authentication state of the mobile station between the ANSI-41 HLR/AC and the GPRS HLR/AUC.